On 16/04/10 10:41, Peter Bex wrote:
Hi all,
I have a table with three columns: one integer and two doubles.
There are two indexes defined (one on the integer and one on one
of the doubles). This table stores 700000 records, which take up
30 Mb according to pg_relation_size(), and the total relation size
is 66 Mb.
[snip]
Is there a way to reduce the per-tuple storage overhead?
Short answer - no.
The database has to track visibility of every row - when it was
inserted, deleted etc to support the MVCC concurrency system.
http://www.postgresql.org/docs/8.4/static/storage-page-layout.html
That means 24 bytes of overhead (on most systems) for each row. That's
higher than some other RDBMS but they'll all have some overhead.
The reason I'm asking is that I have tons of tables like this,
and some data sets are much bigger than this. In a relatively
simple testcase I'm importing data from text files which are
5.7 Gb in total, and this causes the db size to grow to 34Gb.
Anything from double to ten times the size isn't unexpected, depending
on row-sizes and how many indexes you are talking about.
--
Richard Huxton
Archonet Ltd
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